Initial Appearance of Highly Charged Ions from Magnesium Surfaces Irradiated by Q-Switched Ruby Pulses,

The time development of line radiation emitted from a plasma produced by focusing a Q-switched ruby laser onto a solid magnesium target has been investigated in the vacuum-ultraviolet wavelength region using a 2 m grazing incidence monochromator. The electron temperature was obtained using the foil-absorption method. The time of appearance of Mg IX and Mg X ions at the target was measured as a function of the laser power. It was found, that with increasing power the ions appear earlier, Mg IX before Mg X, until for the higher powers used they appeared at about the same time, 2 nsec after the beginning of the laser pulse. The ionization processes occurring in front of the target are discussed using a simple model for the plasma. From the time of appearance of the lines conclusions on the electron temperature in the heating zone can be drawn as well as on an overall heating rate. Author